Whoopie pies with peanut butter filling

I'd never eaten or made whoopie pie before, until now...

I suppose I never really came across them and not being a huge buttercream fanatic, they haven't been on my radar.  I also thought they would be tricky to make.  I'm glad to learn that they're actually not tricky to make, even without special equipment like a whoopie pie pan.

So while whoopie pies have been something of a mystery to me, I came to realize that they're just this funny amalgamation of cake, cookie, and cupcake.  You basically have two cakes in the guise of cookies sandwiched together with a filling or frosting in the center.  In this case, this moist, fluffy chocolate cake is sandwiched with a peanut butter filling.

When I saw this whoopie pie recipe, with the peanut butter filling, in Baking Chez Moi (so many great recipes in that book!), I knew it was a good one for me to make. This girl loves peanut butter, and that flavor is the star of the show here.  The chocolate cake is perfectly soft, moist, and fluffy - and would, in fact, be great for any number of buttercream or traditional marshmallow fillings for those looking for something else - but one bite of these and the taste is full-on peanut butter thanks to that creamy filling.

Another thing I realized is you can store whoopie pies in the fridge and they hold well for a few days.  From personal experience, I can tell you they're a great treat for a playdate but they're fun to eat for adults, too!  I'd say this whoopie pie baking-and-eating experiment was a good call.


I've always been vaguely nervous about the whoopie pie-making process, specifically regarding how to get that little domed cake without investing in a special pan.  I used a small ice cream scoop (the one I used holds a little over a tablespoon of batter) and plopped them out onto my baking sheet.

Sometimes we just need to have faith - and a good recipe in hand - and things work out just fine.  You basically can make these any size you like.  Mine baked up about 2 1/2 inches in diameter and I liked that.

The recipe calls for baking one tray at a time and given the need for room to spread (though I tend to be conservative about how much space I leave so you could probably fit more per sheet), that's a bit of time investment.  I made a half recipe so it wasn't too bad but if you decide to bake two trays at a time, rotating the pans midway through baking, I won't tell on you!

Allow the little cakes to cool and then gently remove them from your baking sheet - it was easy to do.  Then on to the filling, which is fairly basic and a simple mix of: creamy peanut butter, butter, confectioners' sugar, and a little vanilla and salt.  

I had a feeling the recipe was a little skimpy on the filling.  I increased the amount slightly (which is really not hard to do since you can add a bit more peanut butter and adjust the consistency with confectioners' sugar to thicken or a splash of milk should you need to loosen it) but I still ran a teeny bit short so I had 2 cakes leftover.

Once you put them together and make these little cake sandwiches, you just can't help but think they're just kind of cute!  And they sure are fun to eat, leaving you with sticky fingers and mouthfuls of soft, spongy chocolate cake and lingering taste of fragrant, creamy peanut butter.  

Incidentally, the recipe has a suggested optional chocolate ganache glaze you could make and dip the tops of your whoopie pies in.  I opted to omit that for a few reasons including the fact that I couldn't see myself handling these soft cakes agilely enough. That said, a thin layer of ganache, maybe not on top but spread onto the flat bottom of one of the cake layers would be a great way to heighten the chocolate flavor.

So now...what do you do when you have a couple of whoopie pie shells left over?  You make a whoopie pie ice cream sandwich, of course!  

This was a no-brainer because the chocolate cake reminds me of a fluffier version of your traditional ice cream sandwiches - the rectangle ones made with that chocolate cake biscuit with the little holes in them.  I went a little overboard on the ice cream in this ice cream sandwich but it was yummy!

Recipe:

Whoopie Pies with Peanut Butter Filling
Adapted from Baking Chez Moi by Dorie Greenspan

- Makes approximately 22 whoopie pies, depending on size - 

For whoopie pies:
2 cups (272 grams) all-purpose flour
1/2 cup (42 grams) unsweetened cocoa powder (preferably, Dutch-processed)
1 1/4 teaspoon baking soda
1/4 teaspoon baking powder
1/2 teaspoon fine sea salt
1 stick (113 grams) unsalted butter, at room temperature
1/2 cup (100 grams) sugar
1/2 cup (100 grams) packed light-brown sugar
1 large egg, at room temperature
1/2 teaspoon vanilla extract
1 cup (240 ml) whole milk, at room temperature

For peanut butter filling*:
3/4 stick (6 tablespoons; 85 grams) unsalted butter, at room temperature
1/2 cup (128 grams) creamy peanut butter (not natural)
1/2 cup (60 grams) confectioners' sugar
1/2 teaspoon vanilla extract
1/4 teaspoon fine sea salt

* If you like a fairly generous amount of filling for your whoopie pies, you might consider making a little extra.  Otherwise, you can always sandwich any extra cakes with ice cream to make "whoopie pie ice cream sandwiches".

Make cakes: Preheat oven to 350 degrees.  Line baking sheets with parchment paper or silicon baking mats.  (If you are using a whoopie pie pan, butter or spray it with cooking spray.)  

Sift flour, cocoa, baking soda, baking powder, and salt together into a bowl.  In the bowl of a stand mixer fitted with a paddle attachment, beat butter at medium-speed until soft and creamy.  Add both sugars and beat until blended, about 2 minutes.  Add egg and beat for 2 minutes.  Beat in vanilla.  Then reduce mixer speed to low and add the dry ingredients alternately with the milk, adding the dry ingredients in 3 additions and the milk in 2, starting and ending with the dry.  Mix only until ingredients are just incorporated.  The batter should look thick, smooth, and silky.

Use a small ice cream scoop (mine holds a little more than 1 tablespoon of batter) and drop mounds of batter onto the prepared baking sheet, leaving 2 inches of space between each.  (If you are using a whoopie pie pan, fill the molds with batter.)  You'll have to work in batches so cover the batter and set aside in between baking.

Bake for 8-10 minutes, until cakes puff and spring back when lightly touched; a cake tester inserted into the center should come out clean.  Remove from the oven and carefully slide the parchment paper or silicon mat with the cakes on top of a wire rack. Let cool 5-10 minutes, then gently remove the cakes and set them on a rack to cool completely.  Repeat with remaining batter, using fully cooled pans to bake each batch.

Make filling: Place all ingredients into the bowl of a stand mixer fitted with the paddle attachment.  Beat on medium-high speed until filling is soft, fluffy, and smooth, about 3 minutes.

Finish whoopie pies: Transfer filling to a piping bag fitted with a plain or star tip, or use a zip-lock bag with a corner snipped off.  Pipe about a tablespoon or so of filling onto the flat side of half the cakes; top each with the other half, flat side down. Gently twist the tops to ease the filling to the edges.  

Store whoopie pies in the refrigerator, in an airtight container.  Bring to room temperature before serving.